Method for transmitting sounding reference signal in multiple antenna wireless communication system and apparatus therefor

ABSTRACT

A method and a user equipment (UE) for transmitting sounding reference signals via multiple antenna ports in a wireless communication system are discussed. The method according to one embodiment includes receiving a parameter via a higher layer; applying a code division multiplexing (CDM) scheme to the sounding reference signals using the parameter; applying a frequency division multiplexing (FDM) scheme to the sounding reference signals when the parameter is a first value; and transmitting the sounding reference signals via the multiple antenna ports.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of co-pending U.S. patent applicationSer. No. 14/842,507 filed on Sep. 1, 2015, which is a Continuation ofU.S. patent application Ser. No. 14/689,651 filed on Apr. 17, 2015 (nowU.S. Pat. No. 9,143,298 issued on Sep. 22, 2015), which is aContinuation of U.S. patent application Ser. No. 14/087,765 filed onNov. 22, 2013 (now U.S. Pat. No. 9,025,696 issued on May 5, 2015), whichis a Continuation of U.S. patent application Ser. No. 13/920,935 filedon Jun. 18, 2013 (now U.S. Pat. No. 8,619,941 issued on Dec. 31, 2013),which is a Continuation of U.S. patent application Ser. No. 13/841,682filed on Mar. 15, 2013 (now U.S. Pat. No. 8,619,940 issued on Dec. 31,2013), which is a Continuation of U.S. patent application Ser. No.13/158,998 filed on Jun. 13, 2011 (now U.S. Pat. No. 8,428,166 issued onApr. 23, 2013), which claims the benefit under 35 U.S.C. §119(e) to U.S.Provisional Application Nos. 61/434,802 filed on Jan. 20, 2011 and61/434,274 filed on Jan. 19, 2011, and under 35 U.S.C. §119(a) to KoreanPatent Application No. 10-2011-0028851 filed on Mar. 30, 2011, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting a sounding referencesignal from a user equipment to a base station in a wirelesscommunication system and an apparatus therefor.

2. Discussion of the Related Art

A 3^(rd) generation partnership project long term evolution(hereinafter, referred to as ‘LTE’) communication system which is anexample of a wireless communication system to which the presentinvention can be applied will be described in brief.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system. The E-UMTS system is an evolvedversion of the conventional UMTS system, and its basic standardizationis in progress under the 3rd Generation Partnership Project (3GPP). TheE-UMTS may also be referred to as a Long Term Evolution (LTE) system.For details of the technical specifications of the UMTS and E-UMTS,refer to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE) 120, basestations (eNode B and eNB) 110 a and 110 b, and an Access Gateway (AG)which is located at an end of a network (E-UTRAN) and connected to anexternal network. The base stations can simultaneously transmit multipledata streams for a broadcast service, a multicast service and/or aunicast service.

One or more cells may exist for one base station. One cell is set to oneof bandwidths of 1.25, 2.5, 5, 10, and 20 Mhz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to indicate time and frequencydomains to which data will be transmitted and information related toencoding, data size, hybrid automatic repeat and request (HARQ). Also,the base station transmits uplink (UL) scheduling information of uplinkdata to the corresponding user equipment to indicate time and frequencydomains that can be used by the corresponding user equipment, andinformation related to encoding, data size, HARQ. An interface fortransmitting user traffic or control traffic can be used between thebase stations. A Core Network (CN) may include the AG and a network nodeor the like for user registration of the UE. The AG manages mobility ofa UE on a Tracking Area (TA) basis, wherein one TA includes a pluralityof cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology is required for competitiveness in thefuture. In this respect, reduction of cost per bit, increase ofavailable service, use of adaptable frequency band, simple structure,open type interface, proper power consumption of user equipment, etc.are required.

Recently, the standardization project for the subsequent technology ofthe LTE is in progress under the 3GPP. In this specification, thistechnology will be referred to as “LTE-Advanced” or “LTE-A”. The LTEsystem is different from the LTE-A system in that it supports uplinktransmission by using a MIMO antenna scheme.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a methodfor transmitting a sounding reference signal in a MIMO antenna awireless communication system and an apparatus therefor, whichsubstantially obviate one or more problems due to limitations anddisadvantages of the related art.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for transmitting a sounding reference signal from a userequipment in a MIMO antenna wireless communication system comprisesreceiving sounding reference signal setup information from a basestation, the sounding reference signal setup information including aninitial cyclic shift value n_(SRS) ^(cs) and an initial transmissionCombparameter value k _(TC); setting an interval between cyclic shift valuescorresponding to each antenna port based on the initial cyclic shiftvalue, to reach a maximum interval; setting a transmissionComb parametervalue corresponding to a specific one of the antenna ports to a valuedifferent from the initial transmissionComb parameter value if theinitial cyclic shift value is a previously set value and the number ofantenna ports is 4; and transmitting the sounding reference signal tothe base station through each antenna port by using the set cyclic shiftvalue and transmissionComb parameter value.

In another aspect of the present invention, a user equipment of a MIMOantenna wireless communication system comprises a receiving modulereceiving sounding reference signal setup information from a basestation, the sounding reference signal setup information including aninitial cyclic shift value n_(SRS) ^(cs) and an initial transmissionCombparameter value k _(TC); a processor setting an interval between cyclicshift values corresponding to each antenna port based on the initialcyclic shift value, to reach a maximum interval, and setting atransmissionComb parameter value corresponding to a specific one of theantenna ports to a value different from the initial transmissionCombparameter value if the initial cyclic shift value is a previously setvalue and the number of antenna ports is 4; and a transmitting moduletransmitting the sounding reference signal to the base station througheach antenna port by using the set cyclic shift value andtransmissionComb parameter value. In this case, the initialtransmissionComb parameter value k _(TC) is 0 or 1, and the valuedifferent from the transmissionComb parameter value is defined as 1−k_(TC).

Preferably, the initial cyclic shift value n_(SRS) ^(cs) is a randominteger between 0 and 7.

More preferably, the previously set cyclic shift value n_(SRS) ^(cs) isa random integer between 4 and 7, and the specific antenna port has anindex {tilde over (p)} of 1 or 3.

A transmissionComb parameter value k_(TC) ^((p)) allocated to theantenna port index {tilde over (p)} is determined in accordance with thefollowing Equation:

$k_{TC}^{(p)} = \left\{ {\begin{matrix}{1 - {\overset{\_}{k}}_{TC}} & {{{if}\mspace{14mu} n_{SRS}^{cs}} \in {\left\{ {4,5,6,7} \right\} \mspace{14mu} {and}\mspace{14mu} \overset{\sim}{p}} \in \left\{ {1,3} \right\}} \\{\overset{\_}{k}}_{TC} & {otherwise}\end{matrix}.} \right.$

According to the embodiments of the present invention, the userequipment can effectively transmit a sounding reference signal to thebase station in a wireless communication system.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a mobile communication system;

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard;

FIG. 3 is a diagram illustrating physical channels used in a 3GPP systemand a general method for transmitting a signal using the physicalchannels;

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system;

FIG. 5 is a diagram illustrating a structure of an uplink subframe usedin an LTE system;

FIG. 6 is a diagram illustrating another structure of an uplink subframeused in an LTE system;

FIG. 7 is a schematic diagram illustrating a MIMO antenna communicationsystem according to the present invention; and

FIG. 8 is a block diagram illustrating a communication transceiveraccording to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, structures, operations, and other features of the presentinvention will be understood readily by the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to 3GPP system.

Hereinafter, a system that includes a system band of a single frequencyblock will be referred to as a legacy system or a narrowband system. Bycontrast, a system that includes a system band of a plurality offrequency blocks and uses at least one or more frequency blocks as asystem block of a legacy system will be referred to as an evolved systemor a wideband system. The frequency block used as a legacy system blockhas the same size as that of the system block of the legacy system. Onthe other hand, there is no limitation in sizes of the other frequencyblocks. However, for system simplification, the sizes of the otherfrequency blocks may be determined based on the size of the system blockof the legacy system. For example, the 3GPP LTE system and the 3GPPLTE-A system are evolved from the legacy system.

Based on the aforementioned definition, the 3GPP LTE system will hereinbe referred to as an LTE system or a legacy system. Also, a userequipment that supports the LTE system will be referred to as an LTEuser equipment or a legacy user equipment. The 3GPP LTE-A system will bereferred to as an LTE-A system or an evolved system. Also, a userequipment that supports the LTE-A system will be referred to as an LTE-Auser equipment or an evolved user equipment.

For convenience, although the embodiment of the present invention willbe described based on the LTE system and the LTE-A system, the LTEsystem and the LTE-A system are only exemplary and can be applied to allcommunication systems corresponding to the aforementioned definition.Also, although the embodiment of the present invention will herein bedescribed based on FDD mode, the FDD mode is only exemplary and theembodiment of the present invention can easily be applied to H-FDD modeor TDD mode.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard. The controlplane means a passageway where control messages are transmitted, whereinthe control messages are used in the user equipment and the network tomanage call. The user plane means a passageway where data generated inan application layer, for example, voice data or Internet packet dataare transmitted.

A physical layer as the first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access control layer above the physical layervia a transport channel. Data are transferred between the medium accesscontrol layer and the physical layer via the transport channel. Data aretransferred between one physical layer of a transmitting side and theother physical layer of a receiving side via the physical channel. Thephysical channel uses time and frequency as radio resources.Specifically, the physical channel is modulated in accordance with anorthogonal frequency division multiple access (OFDMA) scheme in adownlink, and is modulated in accordance with a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink.

A medium access control layer of the second layer provides a service toa radio link control (RLC) layer above the MAC layer via logicalchannels. The RLC layer of the second layer supports reliable datatransfer. The RLC layer may be implemented as a functional block insidethe MAC layer. In order to effectively transmit IP packets such as IPv4or IPv6 within a radio interface having a narrow bandwidth, a packetdata convergence protocol (PDCP) layer of the second layer performsheader compression to reduce the size of unnecessary controlinformation.

A radio resource control (hereinafter, abbreviated as ‘RRC’) layerlocated on the lowest part of the third layer is defined in the controlplane only. The RRC layer is associated with configuration,re-configuration and release of radio bearers to be in charge ofcontrolling the logical, transport and physical channels. In this case,the radio bearer means a service provided by the second layer for thedata transfer between the user equipment and the network. To this end,the RRC layer of the user equipment and the network exchanges RRCmessage with each other. If the RRC layer of the user equipment is RRCconnected with the RRC layer of the network, the user equipment is inRRC connected mode. If not so, the user equipment is in RRC idle mode. Anon-access stratum (NAS) layer located above the RRC layer performsfunctions such as session management and mobility management.

One cell constituting a base station (eNB) is established at one ofbandwidths of 1.25, 2.5, 5, 10, 15, and 20 Mhz and provides a downlinkor uplink transmission service to several user equipments. At this time,different cells can be established to provide different bandwidths.

As downlink transport channels carrying data from the network to theuser equipment, there are provided a broadcast channel (BCH) carryingsystem information, a paging channel (PCH) carrying paging message, anda downlink shared channel (SCH) carrying user traffic or controlmessages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted via the downlink SCH or anadditional downlink multicast channel (MCH). Meanwhile, as uplinktransport channels carrying data from the user equipment to the network,there are provided a random access channel (RACH) carrying an initialcontrol message and an uplink shared channel (UL-SCH) carrying usertraffic or control message. As logical channels located above thetransport channels and mapped with the transport channels, there areprovided a broadcast control channel (BCCH), a paging control channel(PCCH), a common control channel (CCCH), a multicast control channel(MCCH), and a multicast traffic channel (MTCH).

FIG. 3 is a diagram illustrating physical channels used in a 3GPP systemand a general method for transmitting a signal using the physicalchannels.

The user equipment performs initial cell search such as synchronizingwith the base station when it newly enters a cell or the power is turnedon (S301). To this end, the user equipment synchronizes with the basestation by receiving a primary synchronization channel (P-SCH) and asecondary synchronization channel (S-SCH) from the base station, andacquires information of cell ID, etc. Afterwards, the user equipment canacquire broadcast information within the cell by receiving a physicalbroadcast channel from the base station. Meanwhile, the user equipmentcan identify the status of a downlink channel by receiving a downlinkreference signal (DL RS) in the initial cell search step.

The user equipment which has finished the initial cell search canacquire more detailed system information by receiving a physicaldownlink shared channel (PDSCH) in accordance with a physical downlinkcontrol channel (PDCCH) and information carried in the PDCCH (S302).

Meanwhile, if the user equipment initially accesses the base station, orif there is no radio resource for signal transmission, the userequipment performs a random access procedure (RACH) for the base station(S303 to S306). To this end, the user equipment transmits a preamble ofa specific sequence through a physical random access channel (PRACH)(S303 and S305), and receives a response message to the preamble throughthe PDCCH and the PDSCH corresponding to the PDCCH (S304 and S306). Incase of a contention based RACH, a contention resolution procedure canbe performed additionally.

The user equipment which has performed the aforementioned steps receivesthe PDCCH/PDSCH (S307) and transmits a physical uplink shared channel(PUSCH) and a physical uplink control channel (PUCCH) (S308), as ageneral procedure of transmitting uplink/downlink signals. Controlinformation transmitted from the user equipment to the base station orreceived from the base station to the user equipment through the uplinkincludes downlink/uplink ACK/NACK signals, a channel quality indicator(CQI), a precoding matrix index (PMI), and a rank indicator (RI). Incase of the 3GPP LTE system, the user equipment transmits theaforementioned control information such as CQI/PMI/RI through the PUSCHand/or the PUCCH.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, the radio frame has a length of 10 ms(327200·T_(s)) and includes 10 subframes of an equal size. Each subframe has a length of 1 ms and includes two slots. Each slot has alength of 0.5 ms (15360·T_(s)). In this case, T_(s) represents asampling time, and is expressed by T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸(about 33 ns). The slot includes a plurality of OFDM symbols or SC-FDMAsymbols in a time domain, and includes a plurality of resource blocks(RBs) in a frequency domain. In the LTE system, one resource blockincludes twelve (12) subcarriers×seven (or six) OFDM symbols. Atransmission time interval (TTI), which is a transmission unit time ofdata, can be determined in a unit of one or more subframes. Theaforementioned structure of the radio frame is only exemplary, andvarious modifications can be made in the number of subframes included inthe radio frame or the number of slots included in the subframe, or thenumber of OFDM symbols or SC-FDMA symbols included in the slot.

FIG. 6 is a diagram illustrating a structure of an uplink subframe usedin an LTE system.

Referring to FIG. 6, a subframe 600 having a length of 1 ms, which is abasic unit of LTE uplink transmission, includes two slots 601 of 0.5 ms.In case of normal cyclic prefix (CP) length, each slot includes sevensymbols 602, each of which corresponds to each SC-FDMA symbol. Aresource block 603 is a resource allocation unit corresponding to twelve(12) subcarriers in a frequency domain and one slot in a time domain. Astructure of an LTE uplink subframe is classified into a data region 604and a control region 605. In this case, the data region means a seriesof communication resources used for transmission of data such as voiceand packet transmitted to each user equipment, and corresponds to theother resources except for the control region within the subframe. Thecontrol region means a series of communication resources used fortransmission of downlink channel quality report, ACK/NACK of a downlinksignal, and uplink scheduling request from each user equipment.

As illustrated in FIG. 6, an interval 606 for which a sounding referencesignal can be transmitted within one subframe is a duration whereSC-FDMA symbol at the last location on a time axis of one subframeexists, and the sounding reference signal is transmitted through a datatransmission band on a frequency axis. Sounding reference signals ofseveral user equipments, which are transmitted to the last SC-FDMA ofthe same subframe, can be identified depending on the frequencylocation.

The sounding reference signal includes a constant amplitude zero autocorrelation (CAZAC) sequence. The sounding reference signals transmittedfrom a plurality of user equipments are CAZAC sequencesr^(SRS)(n)=r_(u,v) ^((α))(n) having different cyclic shift values αbased on the following Equation 1.

$\begin{matrix}{\alpha = {2\pi \frac{n_{SRS}^{cs}}{8}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the Equation 1, n_(SRS) ^(cs) is a value set for each user equipmentby the upper layer, and has an integer value between 0 and 7.Accordingly, the cyclic shift value may have eight values depending onn_(SRS) ^(cs).

The CAZAC sequences generated through cyclic shift from one CAZACsequence are characterized in that they have a zero-correlation valuewith the sequences having different cyclic shift values. The soundingreference signals of the same frequency domain can be identified fromone another depending on the CAZAC sequence cyclic shift value by usingthe above characteristic. The sounding reference signal of each userequipment is allocated on the frequency depending on a parameter set bythe base station. The user equipment performs frequency hopping of thesounding reference signal to transmit the sounding reference signal toall of uplink data transmission bandwidths.

Hereinafter, a detailed method for mapping a physical resource fortransmitting a sounding reference signal in an LTE system will bedescribed.

After being multiplied by an amplitude scaling parameter β_(SRS) tosatisfy the transmission power P_(SRS) of the user equipment, thesounding reference signal sequence r^(SRS)(n) is mapped into a resourceelement (RE) having an index of (k, l) from r^(SRS)(0) by the followingEquation 2.

$\begin{matrix}{a_{{{2k} + k_{0}},l} = \left\{ \begin{matrix}{\beta_{SRS}{r^{SRS}(k)}} & {{k = 0},1,\; \cdots \mspace{14mu},{M_{{sc},b}^{RS} - 1}} \\0 & {otherwise}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the Equation 2, k₀ denotes a frequency domain start point of thesounding reference signal, and is defined by the following Equation 3.

$\begin{matrix}{k_{0} = {k_{0}^{'} + {\sum\limits_{b = 0}^{B_{SRS}}{2M_{{sc},b}^{RS}n_{b}}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In the Equation 3, n_(b) denotes a frequency location index. Also, k′₀for a general uplink subframe is defined by the following Equation 4,and k′₀ for an uplink pilot timeslot (UpPTS) is defined by the followingEquation 5.

$\begin{matrix}{\mspace{79mu} {k_{0}^{'} = {{\left( {\left\lfloor {N_{RB}^{UL}/2} \right\rfloor - {m_{{SRS},0}/2}} \right)N_{SC}^{RB}} + k_{TC}}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \\{k_{0}^{'} = \left\{ \begin{matrix}{{\left( {N_{RB}^{UL} - m_{{SRS},0}^{\max}} \right)N_{sc}^{RB}} + k_{TC}} & {{{if}\mspace{14mu} \left( {{\left( {n_{f\mspace{14mu}}{{mod}2}} \right) \times \left( {2 - N_{SP}} \right)} + t_{RA}^{1}} \right){{mod}2}} = 0} \\k_{TC} & {otherwise}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the Equation 4 and the Equation 5, k_(rc) is a transmissionCombparameter signaled to the user equipment through the upper layer and hasa value of 0 or 1. Also, n_(hf) is 0 at the uplink pilot timeslot of thefirst half frame and 0 at the uplink pilot timeslot of the second halfframe. M_(sc,b) ^(RS) is a length, i.e., bandwidth, of a soundingreference signal sequence, which is expressed in a unit of subcarrierdefined as expressed by the following Equation 6.

M _(sc,b) ^(RS) =m _(SRS,b) N _(sc) ^(RB)/2   [Equation 6]

In the Equation 6, m_(SRS,b) is a value signaled from the base stationdepending on an uplink bandwidth N_(RB) ^(UL) as illustrated in thefollowing Table 1 to Table 4.

In order to acquire m_(SRS,b), a cell specific parameter C_(SRS) havingan integer value between 0 and 7 and a user equipment specific parameterB_(SRS) having an integer value between 0 and 3 are required. Thesevalues C_(SRS) and B_(SRS) are given by the upper layer.

TABLE 1 b_(hop) = 0, 1, 2, 3, and 6 ≦ N_(RB) ^(UL) ≦ 40. SRS SRS- SRS-SRS- SRS- bandwidth Bandwidth Bandwidth Bandwidth Bandwidthconfiguration B_(SRS) = 0 B_(SRS) = 1 B_(SRS) = 2 B_(SRS) = 3 C_(SRS)m_(SRS, b) N_(b) m_(SRS, b) N_(b) m_(SRS, b) N_(b) m_(SRS, b) N_(b) 0 361 12 3 4 3 4 1 1 32 1 16 2 8 2 4 2 2 24 1 4 6 4 1 4 1 3 20 1 4 5 4 1 4 14 16 1 4 4 4 1 4 1 5 12 1 4 3 4 1 4 1 6 8 1 4 2 4 1 4 1 7 4 1 4 1 4 1 41

TABLE 2 b_(hop) = 0, 1, 2, 3, and 40 ≦ N_(RB) ^(UL) ≦ 60. SRS SRS- SRS-SRS- SRS- bandwidth Bandwidth Bandwidth Bandwidth Bandwidthconfiguration B_(SRS) = 0 B_(SRS) = 1 B_(SRS) = 2 B_(SRS) = 3 C_(SRS)m_(SRS, 0) N₀ m_(SRS, 1) N₁ m_(SRS, 2) N₂ m_(SRS, 3) N₃ 0 48 1 24 2 12 24 3 1 48 1 16 3 8 2 4 2 2 40 1 20 2 4 5 4 1 3 36 1 12 3 4 3 4 1 4 32 116 2 8 2 4 2 5 24 1 4 6 4 1 4 1 6 20 1 4 5 4 1 4 1 7 16 1 4 4 4 1 4 1

TABLE 3 b_(hop) = 0, 1, 2, 3, and 60 ≦ N_(RB) ^(UL) ≦ 80. SRS SRS- SRS-SRS- SRS- bandwidth Bandwidth Bandwidth Bandwidth Bandwidthconfiguration B_(SRS) = 0 B_(SRS) = 1 B_(SRS) = 2 B_(SRS) = 3 C_(SRS)m_(SRS, 0) N₀ m_(SRS, 1) N₁ m_(SRS, 2) N₂ m_(SRS, 3) N₃ 0 72 1 24 3 12 24 3 1 64 1 32 2 16 2 4 4 2 60 1 20 3 4 5 4 1 3 48 1 24 2 12 2 4 3 4 48 116 3 8 2 4 2 5 40 1 20 2 4 5 4 1 6 36 1 12 3 4 3 4 1 7 32 1 16 2 8 2 4 2

TABLE 4 b_(hop) = 0, 1, 2, 3, and 80 ≦ N_(RB) ^(UL) ≦ 110. SRS SRS- SRS-SRS- SRS- bandwidth Bandwidth Bandwidth Bandwidth Bandwidthconfiguration B_(SRS) = 0 B_(SRS) = 1 B_(SRS) = 2 B_(SRS) = 3 C_(SRS)m_(SRS, 0) N₀ m_(SRS, 1) N₁ m_(SRS, 2) N₂ m_(SRS, 3) N₃ 0 96 1 48 2 24 24 6 1 96 1 32 3 16 2 4 4 2 80 1 40 2 20 2 4 5 3 72 1 24 3 12 2 4 3 4 641 32 2 16 2 4 4 5 60 1 20 3 4 5 4 1 6 48 1 24 2 12 2 4 3 7 48 1 16 3 8 24 2

As described above, the user equipment can perform frequency hopping ofthe sounding reference signal to transmit the sounding reference signalto all the uplink data transmission bandwidths. The frequency hopping isset by a parameter b_(hop) having a value of 0 to 3 given by the upperlayer.

If frequency hopping of the sounding reference signal is not activated,i.e., in case of b_(hop)≧B_(SRS), the frequency location index n_(b) hasa constant value as expressed by the following Equation 7. In theEquation 7, n_(RRC) is a parameter given by the upper layer.

n _(b)=└4n _(RRC) /m _(SRS,b)┘mod N _(b)   [Equation 7]

Meanwhile, if frequency hopping of the sounding reference signal isactivated, i.e., in case of b_(hop)<B_(SRS), the frequency locationindex n_(b) is defined by the following Equations 8 and 9.

$\begin{matrix}{\mspace{79mu} {n_{b} = \left\{ \begin{matrix}{\left\lfloor {4{n_{RRC}/m_{{SRS},b}}} \right\rfloor {mod}\; N_{b}} & {b \leq b_{hop}} \\{\left\{ {{F_{b}\left( n_{SRS} \right)} + \left\lfloor {4{n_{RRC}/m_{{SRS},b}}} \right\rfloor} \right\} \; {mod}\; N_{b}} & {otherwise}\end{matrix} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack \\{{F_{b}\left( n_{SRS} \right)} = \left\{ \begin{matrix}{{\left( {N_{b}/2} \right)\left\lfloor \frac{n_{SRS}{mod}\mspace{11mu} \Pi_{{b'} = b_{hop}}^{b}N_{b'}}{\Pi_{{b'} = b_{hop}}^{b - 1}N_{b'}} \right\rfloor} + \left\lfloor \frac{n_{SRS}\; {mod}{\; \;}\Pi_{{b'} = b_{hop}}^{b}N_{b'}}{2\Pi_{{b'} = b_{hop}}^{b - 1}N_{b'}} \right\rfloor} & {{if}\mspace{14mu} N_{b}{\mspace{11mu} \;}{even}} \\{\left\lfloor {N_{b}/2} \right\rfloor \left\lfloor {{n_{SRS}/\Pi_{{b'} = b_{hop}}^{b - 1}}N_{b'}} \right\rfloor} & {{if}\mspace{14mu} N_{b}{\mspace{11mu} \;}{odd}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

In the Equation 9, n_(SRS) is a parameter that calculates the number oftransmission times of the sounding reference signal and is defined bythe following Equation 10.

$\begin{matrix}{n_{SRS} = \left\{ \begin{matrix}{{{2N_{SP}n_{f}} + {2\left( {N_{SP} - 1} \right)\left\lfloor \frac{n_{s}}{10} \right\rfloor} + \left\lfloor \frac{T_{offset}}{T_{{offset}\_ \max}} \right\rfloor},} \\{\left. {\left\lfloor {{n_{f} \times 10} + \left\lfloor {n_{s}/12} \right\rfloor} \right)/T_{SRS}} \right\rfloor,}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

for 2 ms SRS periodicity of TDD frame structure otherwise

In the Equation 10, T_(SRS) is a period of the sounding referencesignal, and T_(offset) denotes subframe offset of the sounding referencesignal. Also, n_(s) denotes a slot number, and n_(f) denotes a framenumber.

A user equipment specific sounding reference signal setup index I_(SRS)for setting the period T_(SRS) of the user equipment specific soundingreference signal and the subframe offset T_(offset) is expressed asillustrated in the following Table 5 and Table 6 depending on FDD andTDD. In particular, Table 5 illustrates the user equipment specificsounding reference signal setup index in case of the FDD, and Table 6illustrates the user equipment specific sounding reference signal setupindex in case of the TDD.

TABLE 5 SRS Configuration Index SRS Periodicity T_(SRS) SRS I_(SRS) (ms)Subframe Offset T_(offset) 0-1 2 I_(SRS) 2-6 5 I_(SRS) - 2  7-16 10I_(SRS) - 7 17-36 20 I_(SRS) - 17 37-76 40 I_(SRS) - 37  77-156 80I_(SRS) - 77 157-316 160 I_(SRS) - 157 317-636 320 I_(SRS) - 317 637-1023 Reserved reserved

TABLE 6 SRS Periodicity T_(SRS) SRS Configuration Index I_(SRS) (ms)Subframe Offset T_(offset) 0 2 0, 1 1 2 0, 2 2 2 1, 2 3 2 0, 3 4 2 1, 35 2 0, 4 6 2 1, 4 7 2 2, 3 8 2 2, 4 9 2 3, 4 10-14 5 I_(SRS) - 10 15-2410 I_(SRS) - 15 25-44 20 I_(SRS) - 25 45-84 40 I_(SRS) - 45  85-164 80I_(SRS) - 85 165-324 160 I_(SRS) - 165 325-644 320 I_(SRS) - 325 645-1023 Reserved reserved

Hereinafter, a MIMO system will be described. Multiple-InputMultiple-Output (MIMO) means a scheme that a plurality of transmittingantennas and a plurality of receiving antennas are used. Datatransmission and reception efficiency can be improved by the MIMOscheme. Namely, a transmitter or receiver of a wireless communicationsystem can enhance capacity and improve throughput by using a pluralityof antennas. Hereinafter, MIMO may be referred to as ‘MIMO antenna’.

The MIMO antenna technology does not depend on a signal antenna path toreceive a whole message. Instead, in the MIMO antenna technology, datafragments received from a plurality of antennas are incorporated tocomplete data. If the MIMO antenna technology is used, a datatransmission rate can be improved within a specific sized cell region,or system coverage can be enhanced with a specific data transmissionrate. Also, the MIMO antenna technology can widely be used for a userequipment for mobile communication and a relay station. According to theMIMO antenna technology, it is possible to overcome limitation of atransmission rate in mobile communication according to the related artwhere a single antenna is used.

A schematic diagram of a MIMO communication system described in thepresent invention is illustrated in FIG. 7. Referring to FIG. 7, N_(T)number of transmitting antennas are provided at a transmitter whileN_(R) number of receiving antennas are provided at a receiver. If aplurality of antennas are used at both the transmitter and the receiver,theoretical channel transmission capacity is more increased than that aplurality of antennas are used at any one of the transmitter and thereceiver. Increase of the channel transmission capacity is proportionalto the number of antennas. Accordingly, the transmission rate isimproved, and frequency efficiency is also improved. Supposing that amaximum transmission rate is R_(O) when a single antenna is used, atransmission rate corresponding to a case where multiple antennas areused can be increased theoretically as expressed by the followingEquation 11 as much as a value obtained by multiplying a maximumtransmission rate R_(O) by a rate increase R_(i). In this case, R_(i)corresponds to a smaller value of N_(T) and N_(R).

R _(i)=min(N _(T) , N _(R))   [Equation 11]

For example, in a MIMO communication system that uses four transmittingantennas and four receiving antennas, a transmission rate four timesgreater than that of a single antenna system can be obtained. After suchtheoretical capacity increase of the MIMO system has been proved in themiddle of 1990, various technologies have been actively studied tosubstantially improve a data transmission rate. Some of the technologieshave been already reflected in the standard of various wirelesscommunications such as third generation mobile communication and nextgeneration wireless LAN.

Upon reviewing the recent trend of studies related to the MIMO system,active studies are ongoing in view of various aspects such as the studyof information theoretical aspect related to MIMO communication capacitycalculation under various channel environments and multiple accessenvironments, the study of radio channel measurement and model of a MIMOsystem, and the study of time space signal processing technology forimprovement of transmission reliability and transmission rate.

In order to describe a communication method in a MIMO system in moredetail, mathematical modeling of the communication method can beexpressed as follows. As illustrated in FIG. 7, it is assumed that N_(T)number of transmitting antennas and N_(R) number of receiving antennasexist. First of all, a transmitting signal will be described. If thereexist N_(T) number of transmitting antennas, since the number of maximumtransmission information is N_(T), the transmission information can beexpressed by a vector shown in Equation 12 as follows.

s=└s₁, s₂, . . . , s_(N) _(T) ┘^(T)   [Equation 12]

Meanwhile, different kinds of transmission power can be applied to eachof the transmission information s₁, s₂, . . . , s_(N) _(T) . At thistime, supposing that each transmission power is P₁, P₂, . . . , P_(N)_(T) , transmission information of which transmission power iscontrolled can be expressed by a vector shown in Equation 13 as follows.

ŝ=[ŝ₁, ŝ₂, . . . , ŝ_(N) _(T) ]^(T)=[P₁s₁, P₂s₂, . . . , P_(N) _(T)s_(N) _(T) ]^(T)

Also, Ŝ can be expressed by Equation 14 below using a diagonal matrix P.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \cdots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}S_{1} \\S_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Meanwhile, it is considered that a weight matrix W is applied to theinformation vector Ŝ of which transmission power is controlled, so as toobtain N_(T) transmitting signals x₁, x₂, . . . , x_(N) _(T) . In thiscase, the weight matrix serves to properly distribute the transmissioninformation to each antenna depending on a transmission channel status.Such transmitting signals x₁, x₂, . . . , x_(N) _(T) can be expressed byEquation 15 below using a vector X. In this case, W_(ij) means a weightvalue between the ith transmitting antenna and the jth information. Wmay be referred to as a weight matrix or precoding matrix.

$\begin{matrix}{x = {{{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix}\begin{bmatrix}w_{11} & w_{12} & \cdots & w_{1N_{T}} \\w_{21} & w_{22} & \cdots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i1} & w_{i2} & \cdots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \cdots & w_{N_{T}N_{T}}\end{bmatrix}}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}} & \left\lbrack {{Equation}\mspace{14mu} 15} \right\rbrack\end{matrix}$

Generally, a rank in the channel matrix may physically mean the maximumnumber of rows or columns that can transmit different kinds ofinformation from a given channel. Accordingly, since a rank of thechannel matrix is defined by a minimum number of independent rows orcolumns, it is not greater than the number of rows or columns. Forexample, a rank H of the channel matrix H is restricted as illustratedin Equation 16 below.

rank(H)≦min(N _(T) , N _(R))   [Equation 16]

Also, different kinds of information transmitted using the MIMOtechnology will be defined as ‘transport stream’ or more simply as‘stream’. This stream may be referred to as a ‘layer’. In this case, thenumber of transport streams cannot be greater than the rank of thechannel, which corresponds to the maximum number that can transmitdifferent kinds of information. Accordingly, the channel matrix H can beexpressed by the following Equation 17.

# of streams≦rank(H)≦min(N _(T) , N _(R))   [Equation 17]

In this case, “# of streams” represents the number of streams.Meanwhile, it is to be understood that one stream can be transmittedthrough one or more antennas.

Various methods for corresponding one or more streams to severalantennas can exist. These methods can be described, as follows,depending on the types of the MIMO technology. If one stream istransmitted through several antennas, it may be regarded as a spatialdiversity scheme. If several streams are transmitted through severalantennas, it may be regarded as a spatial multiplexing scheme. Ofcourse, a hybrid scheme of the spatial diversity scheme and the spatialmultiplexing scheme can exist.

Since the current LTE system does not support uplink MIMO transmission,a problem occurs in that there is no method for transmitting a soundingreference signal using multiple antennas. In order to solve thisproblem, the present invention suggests a method for allocating atransmissionComb parameter k_(TC) and a cyclic shift value α of thesounding reference signal used in each antenna based on n_(SRS) ^(cs)(in this case, n_(SRS) ^(cs) has an integer value between 0 and 7)signaled through the upper layer.

First Embodiment

First of all, the first embodiment suggests that sounding referencesignals used in respective antennas are set to have cyclic shift valuesof the maximum interval. In more detail, a cyclic shift value of each ofthe transmitting antennas can be set based on the following Equation 18depending on a total of transmitting antennas.

$\begin{matrix}{n_{{SRS}\_ k}^{cs} = {\left\{ {n_{SRS}^{cs} + {\frac{{CS}_{total}}{{the}\mspace{14mu} {total}\mspace{14mu} \# \mspace{11mu} {of}\mspace{14mu} {transmit}\mspace{14mu} {antenna}} \cdot \left( {k - 1} \right)}} \right\} {{mod}{CS}}_{total}}} & \left\lbrack {{Equation}\mspace{14mu} 18} \right\rbrack\end{matrix}$

In the Equation 18, k denotes transmitting antenna index, n_(SRS) _(_)_(k) ^(cs) denotes a cyclic shift value allocated to the transmittingantenna of the index k, and CS_(total) denotes a maximum number ofcyclic shift values. In particular, the transmitting antenna index is aninteger greater than 0, preferably an integer more than 1. Also, thecyclic shift values allocated from the sounding reference signals areintegers between 0 and 7. Since a total of eight cyclic shift values areobtained, CS_(total) has a value of 8.

Examples of the cyclic shift values allocated to the respectivetransmitting antennas in accordance with the Equation 18 when the numberof the transmitting antennas is 2 and 4 are illustrated in Table 7 andTable 8, respectively.

TABLE 7 Cyclic shift value for Cyclic shift value for n_(SRS) ^(cs)antenna port 0 antenna port 1 0 0 4 1 1 5 2 2 6 3 3 7 4 4 0 5 5 1 6 6 27 7 3

TABLE 8 Cyclic Cyclic shift value shift value for antenna for antennaCyclic shift value Cyclic shift value n_(SRS) ^(cs) port 0 port 1 forantenna port 2 for antenna port 3 0 0 2 4 6 1 1 3 5 7 2 2 4 6 0 3 3 5 71 4 4 6 0 2 5 5 7 1 3 6 6 0 2 4 7 7 1 3 5

Next, the present invention suggests that the transmissionComb parameterand the cyclic shift value allocated to each antenna are set based onone value of n_(SRS) ^(cs) and one value of k_(TC) signaled from theupper layer. Also, the present invention suggests that differenttransmissionComb parameters or the same transmission Comb parameterk_(TC) is allocated to each antenna for transmitting a soundingreference signal if the sounding reference signal is transmitted to fourtransmitting antennas considering that orthogonality between thesounding reference signals transmitted to different antennas may bedestroyed due to increase of delay spread. In other words, a codedivision multiplexing scheme having different cyclic shift valuesbetween the respective antennas is applied to specific values n_(SRS)^(cs) based on initial cyclic shift values n_(SRS) ^(cs) (in this case,n_(SRS) ^(cs) has integer values between 0 and 7) signaled through theupper layer, whereby the same transmissionComb parameter k_(TC) isallocated to each antenna. In order to prevent orthogonality, which mayoccur between the respective antennas due to increase of delay spreadduring sounding reference signal transmission, from being destroyed, acode division multiplexing scheme and a frequency division multiplexingscheme are simultaneously applied to another specific values n_(SRS)^(cs), wherein the code division multiplexing scheme allocates differenttransmissionComb parameters to the respective antennas to allow eachantenna to have its respective cyclic shift value different from thoseof the other antennas, and the frequency multiplexing scheme is based ondifferent transmissionComb parameters. In this case, allocation of aseparate transmissionComb parameter to each antenna is applied to thecase where the sounding reference signal is transmitted to fourantennas. However, allocation of a separate transmissionComb parameterto each antenna is not applied to the case where the sounding referencesignal is transmitted to two antennas as the problem of orthogonalitydestruction little occurs.

In more detail, the transmissionComb parameter k_(TC) signaled from theupper layer is set to the initial value, and based on thetransmissionComb parameter k_(TC) signaled from the upper layer, thesame transmissionComb parameter is allocated to each antenna or aseparate transmissionComb parameter is allocated to each antenna. Thefollowing Table 9 Table 12 illustrate the cyclic shift values andtransmissionComb parameters according to the first embodiment of thepresent invention, which are allocated to each antenna depending on thevalue of n_(SRS) ^(cs) in uplink transmission based on four transmittingantennas. In Table 9 to Table 12, the initial value of k_(TC) isexpressed as A. Preferably, the initial value A has a value of 1 or 0.

TABLE 9 CS value Transmission comb value Antenna Antenna Antenna AntennaAntenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1 port = 2port = 3 port = 0 port = 1 port = 2 port = 3 0 0 2 4 6 A A A A 1 1 3 5 7A A A A 2 2 4 6 0 A A A A 3 3 5 7 1 A A A A 4 4 6 0 2 1-A A 1-A A 5 5 71 3 1-A A 1-A A 6 6 0 2 4 1-A A 1-A A 7 7 1 3 5 1-A A 1-A A

TABLE 10 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 2 4 6 A A A A1 1 3 5 7 A A A A 2 2 4 6 0 A A A A 3 3 5 7 1 A A A A 4 4 6 0 2 A A 1-A1-A 5 5 7 1 3 A A 1-A 1-A 6 6 0 2 4 A A 1-A 1-A 7 7 1 3 5 A A 1-A 1-A

TABLE 11 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 2 4 6 A A A A1 1 3 5 7 A A A A 2 2 4 6 0 A A A A 3 3 5 7 1 A A A A 4 4 6 0 2 1-A 1-AA A 5 5 7 1 3 1-A 1-A A A 6 6 0 2 4 1-A 1-A A A 7 7 1 3 5 1-A 1-A A A

TABLE 12 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 2 4 6 A A A A1 1 3 5 7 A A A A 2 2 4 6 0 A A A A 3 3 5 7 1 A A A A 4 4 6 0 2 A 1-A A1-A 5 5 7 1 3 A 1-A A 1-A 6 6 0 2 4 A 1-A A 1-A 7 7 1 3 5 A 1-A A 1-A

Second Embodiment

The second embodiment of the present invention suggests that a cyclicshift value of a maximum distance is allocated to an antenna port 0 andan antenna port 1 in pairs regardless of uplink transmission rank, and acyclic shift value corresponding to an intermediate value of the cyclicshift value allocated to the antenna port 0 and the antenna port 1 isallocated to an antenna port 2 and an antenna port 3 in pairs. Examplesof the cyclic shift values allocated to the respective antenna ports inaccordance with the second embodiment are illustrated in Table 13 below.

TABLE 13 Cyclic Cyclic shift value shift value for antenna for antennaCyclic shift value Cyclic shift value n_(SRS) ^(cs) port 0 port 1 forantenna port 2 for antenna port 3 0 0 4 2 6 1 1 5 3 7 2 2 6 0 4 3 3 7 15 4 4 2 6 0 5 5 1 7 3 6 6 0 4 2 7 7 3 5 1

Also, considering that orthogonality between the sounding referencesignals transmitted to different antennas may be destroyed due toincrease of delay spread based on the cyclic shift value suggested inthe second embodiment, the cyclic shift value and the transmissionCombparameter allocated to each antenna are set based on one value ofn_(SRS) ^(cs) and k_(TC) as illustrated in Table 14 to Table 17 below.In particular, the following Table 14 Table 17 illustrate the cyclicshift values and transmissionComb parameters according to the secondembodiment of the present invention, which are allocated to each antennadepending on the value of n_(SRS) ^(cs) in uplink transmission based onfour transmitting antennas. In Table 14 to Table 17, the initial valueof k_(TC) is expressed as A. Preferably, the initial value A has a valueof 1 or 0.

TABLE 14 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 4 2 6 A A A A1 1 5 3 7 A A A A 2 2 6 0 4 A A A A 3 3 7 1 5 A A A A 4 4 0 6 2 1-A A1-A A 5 5 1 7 3 1-A A 1-A A 6 6 2 4 0 1-A A 1-A A 7 7 3 5 1 1-A A 1-A A

TABLE 15 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 4 2 6 A A A A1 1 5 3 7 A A A A 2 2 6 0 4 A A A A 3 3 7 1 5 A A A A 4 4 0 6 2 A A 1-A1-A 5 5 1 7 3 A A 1-A 1-A 6 6 2 4 0 A A 1-A 1-A 7 7 3 5 1 A A 1-A 1-A

TABLE 16 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 4 2 6 A A A A1 1 5 3 7 A A A A 2 2 6 0 4 A A A A 3 3 7 1 5 A A A A 4 4 0 6 2 1-A 1-AA A 5 5 1 7 3 1-A 1-A A A 6 6 2 4 0 1-A 1-A A A 7 7 3 5 1 1-A 1-A A A

TABLE 17 CS value Transmission comb value Antenna Antenna AntennaAntenna Antenna Antenna Antenna Antenna n_(SRS) ^(cs) port = 0 port = 1port = 2 port = 3 port = 0 port = 1 port = 2 port = 3 0 0 4 2 6 A A A A1 1 5 3 7 A A A A 2 2 6 0 4 A A A A 3 3 7 1 5 A A A A 4 4 2 6 0 A 1-A A1-A 5 5 1 7 3 A 1-A A 1-A 6 6 0 4 2 A 1-A A 1-A 7 7 3 5 1 A 1-A A 1-A

Referring to Table 9 to Table 12 and Table 14 to Table 17, if the sametransmissionComb parameter is used, since each sounding reference signalis identified depending on the cyclic shift value, it is noted that thecode division multiplexing scheme is used. Also, if differenttransmissionComb parameters are used, it is noted that the code divisionmultiplexing scheme and the frequency division multiplexing scheme areused at the same time.

In particular, Table 12 and Table 17 can be expressed by the followingEquation 19.

$\begin{matrix}{k_{TC}^{(p)} = \left\{ \begin{matrix}{1 - {\overset{\_}{k}}_{TC}} & {{{if}\mspace{14mu} n_{SRS}^{cs}} \in {\left\{ {4,5,6,7} \right\} \mspace{14mu} {and}\mspace{14mu} \overset{\sim}{p}} \in \left\{ {1,3} \right\}} \\{\overset{\_}{k}}_{TC} & {otherwise}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 19} \right\rbrack\end{matrix}$

In the Equation 19, k_(TC) ^((p)) denotes a transmissionComb parameterallocated to an antenna port {tilde over (p)}, and k _(TC) means thetransmissionComb parameter k_(TC) conventionally signaled from the upperlayer. In particular, it is noted from the Equation 19 in the samemanner as Table 12 and Table 17 that a transmissionComb parameter 1−k_(TC) not the transmissionComb parameter k _(TC) is allocated to theantenna ports 1 and 3 if the value of n_(SRS) ^(cs) is 4 to 7.

According to the present invention, reference signal multiplexing forsupporting a MIMO antenna scheme in a wireless communication system canbe performed, and more excellent channel estimation throughput can beobtained.

The present invention can be used for the method for transmitting asounding reference signal periodically using multiple antennas in awireless communication system and the method for transmitting a soundingreference signal non-periodically using multiple antennas in a wirelesscommunication system. Additionally, although the present invention hasbeen described that the values of n_(SRS) ^(cs) and k_(TC) are allocatedfrom the upper layer, the principle of the present invention can beapplied to the case where the values of n_(SRS) ^(cs) and k_(TC) aredynamically varied through the PDCCH. Also, although the presentinvention has been described that the initial cyclic shift value ofn_(SRS) ^(cs) is independently allocated for the sounding referencesignal from the upper layer, a method for setting n_(SRS) ^(cs) byreusing a cyclic shift value used for DMRS included in a DCI format 0and a DCI format 4 can also be applied to the present invention.

FIG. 8 is a block diagram illustrating a communication transceiveraccording to the embodiment of the present invention. The transceivermay be a part of the base station and the user equipment.

Referring to FIG. 8, the transceiver 800 includes a processor 810, amemory 820, a radio frequency (RF) module 830, a display module 840, anda user interface module 850.

The transceiver 800 is illustrated for convenience of description, andsome of its modules may be omitted. Also, the transceiver 800 mayfurther include necessary modules. Moreover, some modules of thetransceiver 800 may be divided into segmented modules. The processor 810is configured to perform the operation according to the embodiment ofthe present invention illustrated with reference to the drawings.

In more detail, if the transceiver 800 is a part of the base station,the processor 810 can generate a control signal and map the controlsignal into a control channel configured within a plurality of frequencyblocks. Also, if the transceiver 800 is a part of the user equipment,the processor 810 can identify a control channel allocated thereto,through the signal received from the plurality of frequency blocks, andcan extract a control signal from the control channel.

Afterwards, the processor 810 can perform the necessary operation basedon the control signal. For the detailed operation of the processor 810,refer to the description illustrated in FIG. 1 to FIG. 7.

The memory 820 is connected with the processor 810 and stores anoperating system, an application, a program code, and data therein. TheRF module 830 is connected with the processor 810 and converts abaseband signal to a radio signal or vice versa. To this end, the RFmodule 830 performs analog conversion, amplification, filtering andfrequency uplink conversion, or their reverse processes. The displaymodule 840 is connected with the processor 810 and displays variouskinds of information. Examples of the display module 840 include, butnot limited to, a liquid crystal display (LCD), a light emitting diode(LED), and an organic light emitting diode (OLED). The user interfacemodule 850 is connected with the processor 810, and can be configured bycombination of well known user interfaces such as keypad and touchscreen.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predetermined type.Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The embodiments of the present invention have been described based onthe data transmission and reception between the user equipment and thebase station. A specific operation which has been described as beingperformed by the base station may be performed by an upper node of thebase station as the case may be. In other words, it will be apparentthat various operations performed for communication with the userequipment in the network which includes a plurality of network nodesalong with the base station can be performed by the base station ornetwork nodes other than the base station. The base station may bereplaced with terms such as a fixed station, Node B, eNode B (eNB), andaccess point. Also, the user equipment may be replaced with terms suchas a mobile station (MS) and a mobile subscriber station (MSS).

The embodiments according to the present invention can be implemented byvarious means, for example, hardware, firmware, software, or theircombination. If the embodiment according to the present invention isimplemented by hardware, the embodiment of the present invention can beimplemented by one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, microcontrollers,microprocessors, etc.

If the embodiment according to the present invention is implemented byfirmware or software, the embodiment of the present invention can beimplemented by a type of a module, a procedure, or a function, whichperforms functions or operations described as above. A software code maybe stored in a memory unit and then may be driven by a processor. Thememory unit may be located inside or outside the processor to transmitand receive data to and from the processor through various means whichare well known.

The present invention can be applied to a wireless communication system.In more detail, the present invention can be applied to the method andapparatus for transmitting a sounding reference signal from a userequipment in a wireless communication system that supports MIMO antennatransmission.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

What is claimed is:
 1. A method for transmitting sounding referencesignals via multiple antenna ports by a user equipment (UE) in awireless communication system, the method comprising: receiving aparameter via a higher layer; applying a code division multiplexing(CDM) scheme to the sounding reference signals using the parameter;applying a frequency division multiplexing (FDM) scheme to the soundingreference signals when the parameter is a first value; and transmittingthe sounding reference signals via the multiple antenna ports.
 2. Themethod of claim 1, wherein, when the parameter is a second value, theFDM scheme is not applied to the sounding reference signals.
 3. Themethod of claim 2, wherein the first value is one of integers between 4and 7, and the second values are one of integers between 0 and
 3. 4. Themethod of claim 1, wherein applying the CDM scheme to the soundingreference signals using the parameter comprises generating the soundingreference signals using the parameter.
 5. A user equipment (UE) in awireless communication system, the UE comprising: a processor configuredto: configure a parameter via a higher layer, apply a code divisionmultiplexing (CDM) scheme to sounding reference signals using theparameter, and apply a frequency division multiplexing (FDM) scheme tothe sounding reference signals when the parameter is a first value; anda RF (Radio Frequency) module configured to transmit the soundingreference signals via multiple antenna ports.
 6. The UE of claim 5,wherein, when the parameter is a second value, the FDM scheme is notapplied to the sounding reference signals.
 7. The UE of claim 5, whereinthe first value is one of integers between 4 and 7, and the secondvalues are one of integers between 0 and
 3. 8. The UE of claim 5,wherein the sounding reference signals is generated by using theparameter.